The following pictures show population of bands for materials having different electrical properties. Which of the three types of packing used by metals makes the most efficient use of space and which makes the least efficient use ?įcc has the most efficient packing of particles while scc has the least efficient packing. The smallest constituents or particles of various solids are atoms, ions or molecules. What are the types of particles in each of the four main classes of crystalline solids? Answer the following in one or two sentences. Pb has fcc structure with edge length of unit cell 495 pm. Number of octahedral and tetrahedral voids in 0.5 mole of substance is respectively (d) If the number of atoms is N/2, the number of tetrahedral voids is N.Ī compound forms hcp structure. (c) If the number of atoms is N the number of octahedral voids is 2N. (b) The centres of spheres in octahedral voids are at the a pices of a regular tetrahedron. (a) Four spheres are involved in the formation of tetrahedral void. The coordination number of atoms in bcc crystal lattice is In crystal lattice formed by bcc unit cell the void volume is (d) overall electrical neutrality is preserved (a) electrical neutrality of the substance is changed. The number of oppositely charged ions are appropriately adjusted such that the charges are balanced and the compound formed is electrically neutral.ĭepending on the relative sizes of the cations and anions of the ionic compound, the relatively smaller ion, the cation occupies either tetrahedral or octahedral holes of the crystal lattice.Which of the following is n-type semiconductor? Ionic solids are formed from cations and anions. Want to read about Organic Chemistry, read here. Hence actual volume occupied by one atom of radius r is equal to \( cm\) The total volume of the unit cell contains only one atom of radius r. The volume occupied by unit cell \(V= 8r^3\). Hence the total number of atoms contained by a unit cell is equal to 1/8 x 8 =1 atom. There are eight corners of the simple cubic unit cell. Each corner of the unit cell is shared by eight unit cells i.e each corner of the unit cell effectively contains only 1/8 of the atom. This is the radius of each constituent sphere then it is evident from the figure that a=2r and the volume of unit cell \(V = a^3 = 8r^3\). Simple Cubic CellĬonsider a simple cubic cell with each side of length a unit as shown in the figure. The mass of a unit cell is equal to the product of the number of atoms in a unit cell and the mass of each atom in a unit cell. Density Of Unit Cellĭensity of a unit cell is given as the ratio of mass and volume of unit cell. In this article, we will learn the density of different unit cells like Simple Cubic Cell, body-centred Crystal Structure, Face Centred Cubic Structure with solved examples, Packing In Voids of Ionic Solids and Radius ratio rule for ionic compounds.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |